In a process of preparing a hot beverage, both a temperature of the water and a quantity of the water in relation to a quantity of extractable material are important factors. This is particularly true in the case of a process of preparing coffee on the basis of a quantity of ground coffee beans and hot water. In such a case, a proportion between the quantity of ground coffee beans and a quantity of hot water that is conducted through the ground coffee beans is determinative of the strength and aroma of the coffee.
Usually, coffee is prepared by using a coffee maker. A specific type of coffee maker is a coffee maker which is suitable for preparing quantities of coffee on the basis of coffee pads, i.e. envelopes filled with a quantity of ground coffee beans, wherein the envelopes are permeable to liquid. In general, such a coffee maker comprises a sealable brew chamber which is adapted to receiving one or more coffee pads. During operation of the coffee maker, a quantity of hot water is forced to flow through the at least one coffee pad. In the process, the envelope of the coffee pad acts as a filter. In this way, on the basis of the interaction between the hot water and the coffee pad inside the brew chamber, a desired quantity of coffee is obtained.
For the purpose of heating the water to a predetermined temperature, usually a temperature between 90° C. and 96° C., the coffee maker comprises a boiler having an interior space for containing the water, and heating means for heating the water. For the purpose of realizing a flow of water, the coffee maker comprises a pump. The pump, the boiler and the brew chamber are interconnected by means of tubes for transporting water.
A quantity of coffee that is obtained by using the coffee maker is determined by a quantity of hot water that is conducted through the coffee pad(s) during operation of the coffee maker. In view of the fact that it is desired to let the coffee maker supply predetermined quantities of coffee, which are adapted to the dimensions of a coffee cup or a coffeepot to be used for the purpose of receiving coffee from the coffee maker, and that it is desired to let the coffee maker supply coffee of a predetermined strength and aroma, it is important that the quantity of hot water that is that is conducted through the coffee pad(s) during operation of the coffee maker is accurately controlled.
Methods for controlling the quantity of the hot water that is used for the purpose of preparing a hot beverage on the basis of a predetermined quantity of extractable material are known. In many cases, a beverage maker is equipped with a controlling circuit which is adapted to operating the pump in such a way that a total period during which the pump is operated corresponds to a predetermined period which is representative of a predetermined quantity of water.
For example, U.S. Pat. No. 6,000,317 discloses a coffee maker having a water reservoir for containing cold water, a heating chamber for heating a quantity of water, and a pump for pumping water from the reservoir through the heating chamber to a filter device. During operation of the coffee maker, the actuation of the pump is controlled by a control device. In U.S. Pat. No. 6,000,317, it is noted that if the entire content of the reservoir is to be brewed, a sensor which is responsive to the absence of water may be applied, wherein a signal of this sensor leads to a termination of the operation of the pump. Furthermore, in U.S. Pat. No. 6,000,317, it is noted that in case it is desired to use the coffee maker for preparing coffee by using only a portion of water from the reservoir, the coffee maker may be provided with a control selector for inputting-to the control device the desired quantity of coffee to be brewed. In such case, a flow detector may be provided in a flow path between the reservoir and the filter device, to measure the total flow of water during the process of preparing the coffee. The control device will deactivate the pump when a desired flow has taken place. Alternatively, it is possible that the operating time of the pump is controlled depending upon a desired quantity of coffee to be brewed.